Wikipedia has information on the dates of some of the manufacturers. The address is: http://en.wikipedia.org/wiki/G-1_military_flight_jacket And here is what it says:
The military specifications under which the naval flight jackets were made, in the order of latest to earliest, are

The first Navy designation of "G-1" came under the 55J14 specification.

The earlier jackets are generally considered to be of higher quality than the post-Vietnam era jackets as the earlier jackets were constructed of goatskin and had a real mouton collar. Current model issue jackets (although there are exceptions) are constructed of cowhide and have a synthetic collar.

The makers of the Navy's jackets of the above specifications, in rough chronological order from the current supplier to pre-WWII include:

For a very brief period from 1979 until early 1981, issuance of the G-1 to new USN, USMC and USCG flight crew personnel (i.e., officer flight students and newly-designated enlisted Naval Aircrewman) was discontinued as a budgetary economy action, with those personnel being issued summer weight green Nomex flight jackets identical to those issued to their .S. Air Force counterparts. Replacement of worn out G-1 jackets for extant Naval Aviation personnel was also discontinued during this period. This action was reversed by Secretary of the Navy action in early 1981 and those USN, USMC and USCG flight crew personnel who had not receive G-1 jackets were issued one retroactively.

Modifications to USN, USMC and USCG uniform regulations in the 1990s reduced the type and number of permissible insignia on the G-1, but concurrently permitted wear of the G-1 jacket off base with service uniforms.

Commercial versions of the jacket have been available on the consumer market. Official military suppliers which also sold similar spec jackets to the public include Cockpit USA, Cooper Sportswear, Orchard M/C, Brill Bros, Schott and Excelled. As of 2010 Orchard M/C was still selling 1986 MIL-labeled jackets to the general public. These are new production and come in goatskin and cowhide varieties stamped USN, USCG or USMC. Premium jackets are offered by many companies including Lost Worlds, Gibson and Barnes, and Eastman. L.L.Bean is also selling a mouton insulated version.